LEIGH SALES, PRESENTER: It's one of the most hotly disputed questions in the debate over climate change. Can extreme weather events like bushfires and floods be blamed on global warming?

Scientists have always been cautious about linking any one event to climate change, but now Australia's Climate Commission has joined the dots between a series of a weather-related disasters and global warming in what it calls the nation's "angry summer".

This year was the hottest summer ever recorded in Australia with almost three quarters of the country experiencing extreme temperatures and many places reporting record maximums.

In December, three states, Tasmania, New South Wales and Victoria, battled major bushfires which burnt through thousands of hectares of scrub.

January was the hottest January on record. There were seven days running where the average daily maximum for the country was more than 39 degrees.

Just weeks later, Queensland and much of northern New South Wales were underwater as record rainfalls caused extensive flooding.

The report was released by the Chief Climate Commissioner, Professor Tim Flannery. He joined me in our Sydney studio.

Professor Flannery, in this report, what link are you asserting between extreme weather events over the past summer - fires, floods and so on - and climate change?

TIM FLANNERY, CHIEF CLIMATE COMMISSIONER: Well, look, there are really two aspects to that. One is that everything we're seeing is consistent with what the climate scientists have been telling us now for decades and it's very consistent with the physics and chemistry that we know the way the earth works. But secondly, we've seen 123 records broken and each of those records really takes us into a new climatic territory. And when you get records being broken at that scale, you can start to see a shifting from one climate system to another. So the climate has in one sense actually changed and we are now entering a new series of climatic conditions that we just haven't seen before.

LEIGH SALES: How do you know that the new climatic conditions are responsible for the extreme whether events? How do you know that it's just not some combination of metrological circumstances?

TIM FLANNERY: Sure. Look, the studies suggest it's a 1/500 chance that this sorta stuff is just normal. This is way outside the range of anything we've experienced before. It is really an extraordinary summer. And when you view it in the context of what's happened in the US at the last summer where there was over 3,000 climatic records broken and the Arctic ice conditions again at record lows, you start seeing a pattern, that there's been a shift from a climate where we had quite a number of cool days, quite a number of warm days. Now we're getting far fewer cool days, many, many more warm days and a number of record-breaking hot days.

LEIGH SALES: Haven't we in the past been cautioned not to link individual weather events with climate change? And so for example how do you account for, say, at the moment in the United States where on the East Coast they're standing by for an extreme blizzard, which is unusual for this time of year? Something that would happen more like the dead of winter.

TIM FLANNERY: Well, look, that's a whole very complex issue you've raised there. Just to go back to the point though about is this one event or not: we're not talking about one event here, we're talking about an emerging trend. And we can see that that trend is entirely consistent with what the climate scientists have been saying for years. It's taking us into new climatic territory here in Australia as we break more records. Blizzards: look, we don't know. Is that due to cold conditions or not? Sometimes when you've got very warm oceans, you get a lot of evaporation and you get more snowfall. So I think just to jump to the conclusion that you're seeing a blizzard somewhere, it's not telling you anything, that single event, about the climatic trend.

LEIGH SALES: So does that mean now when people do see an extreme weather event, they can say it's due to climate change, because as I say, in the past we've been cautioned not to leap to that conclusion?

TIM FLANNERY: No, because there are a few well-attested examples in the climate community where we've got a very, very long record, temperature record and a very dense record, say, in Europe, where we can say a single event is due to climate change. But the statistical proof is really burdensome to do that. But that's not what we're seeing here. What we're seeing is a whole slew of new records, new territory, new climatic territory, which we're seeing in Australia and the US and in the Arctic. And that's part of a longer trend, which is very clear, that we're moving from condition where there was quite a number of cool days and a number of warm days to one where there's far fewer cool days and many more warm days and may record-breaking days.

LEIGH SALES: We know that, say, if you look back over the past 50 years there's clear evidence of global warming. You know, the figures go like that. But there were figured released I think late last year that showed that there'd been a plateau for about the past 15 or so years, you know, so it was flatter. So if there's been a plateau in recent years, how come this summer's extreme weather events are due to climate change? Wouldn't you have been seeing those same sorts of events all the way back those 15 years?

TIM FLANNERY: Look, in a sense what you're saying is correct, Leigh, but there has been no plateau. If you look at the temperature of the Earth, we have to measure the oceans, the air and the land. And there, we see a continually strong rise in temperature. 90 per cent of the heat that is trapped by the greenhouse gases goes into the ocean, and you look at the whole of the Earth, we're seeing a very strong warming trend. The atmosphere, you know, it's a very volatile organ of the planet. Sometimes we get cooler average temperatures, sometimes warmer, it bounces around a little bit on the graph. And you can pick any period in that to show anything you want. But if you look at the whole Earth system, you can see that strong warming trend. And indeed, if you look at the atmospheric record for a long enough period, you see exactly the same trend.

LEIGH SALES: The figures that were released last year I think that are the combined Meteorological Office in Britain figures with the East Anglia University, their climate unit, don't they show that the pace of climate change has slowed in recent times? I'm not saying there's no climate change, I'm just say that the pace has slowed.

TIM FLANNERY: Sure. Look, the figures you're referring to are a four-year forecast the Met' Bureau does and they revise that four-year forecast every year. Now last year they just revised it down a built. The warming trend was still there, they just - the amplitude of the change was less due to a series of factors. We've had some - our La Nina years in recent history and that has an influence. So the warming trend is there. People - some people, sceptics and others, try to say otherwise, but in fact if you look at the data, there's no doubt about it. I mean - and it's consistent with the physics. The extra greenhouse gases haven't vanished. The heat imbalance is still there. The heat has to go somewhere.

LEIGH SALES: So what are the implications of both the amplitude of that change that you just mentioned there and then also what you've found in this report today?

TIM FLANNERY: Well, look, we published this report because the Australian public are quite frankly confused with what's happened over this summer. It's been an extraordinary mix of events from recording flooding to record dry spells through to record heat waves and so forth. The report shows how all of that relates to a change in climate due to the increased burden of greenhouse gases. So that's why we published it. It's very important that people like Emergency Services and others understand the full extent of these changes and what to expect in future. And so that's what the report is all about. We will see in coming decades a continuation of that pattern, and unless we manage to reduce greenhouse gas emissions globally, unfortunately, we'll soon an exacerbation of those conditions in future. So, that I guess is the bottom line for the report: that we need to act to continue our reductions we've seen recently globally and get on a more sustainable pathway.